The present invention relates generally to infusion devices for delivering fluids, and more particularly to ambulatory infusion devices and to flow regulators mounted therein.
Ambulatory pumps or infusors are used for delivering a predetermined quantity of a drug or other medication to a patient in a preselected time period (e.g., several hours or days) at a slow fluid flow rate. Such infusors are typically worn on the body of the patient. A conventional infusor, such as that shown in U.S. Pat. No. 5,897,530 (the '530 patent), includes an elastomeric bladder filled with fluid to be infused and a rigid, fluid-tight housing around the bladder. The rigid housing does not conform to the patient's body and thus is uncomfortable. An infusor shown in U.S. Pat. No. 5,284,481 includes a collapsible shell surrounding an elastic reservoir. The ends of the shell and reservoir are attached to rigid end caps which do not conform to the patient's body and are therefore uncomfortable.
The bladder does not provide for constant fluid pressure as the fluid is infused. Indeed, fluid pressure at the outlet of the bladder will tend to be relatively high at the beginning of infusion and again at the end of infusion. This variability of fluid pressure will cause higher flow rates at the beginning and at the end of infusion, which is undesirable.
Conventional infusors such as that shown in the '530 patent include a valve and a glass capillary flow restrictor downstream from the bladder for regulating fluid flow rate. The flow restrictor is relatively expensive due to its glass construction, and can break during shipping and use. The glass capillary is rigid and does not conform to the patient's body, making it uncomfortable.